The present invention relates generally to a reflective lamp utilized in a fluid purification system that maximizes the light delivery to a photocatalytic coating that oxidizes gaseous contaminants that adsorb onto the surface to form carbon dioxide, water, and other substances.
Indoor air can include trace amounts of contaminants, including carbon monoxide and volatile organic compounds such as formaldehyde, toluene, propanal, butene, and acetaldehyde. Absorbent air filters, such as activated carbon, have been employed to remove these contaminants from the air. As air flows through the filter, the filter blocks the passage of the contaminants, allowing contaminant free air to flow from the filter. A drawback to employing filters is that they simply block the passage of contaminants and do not destroy them.
Air purification systems commonly include one lamp or one bank of lamps and one photocatalytic monolith, such as a honeycomb. A photocatalytic coating, such as titanium dioxide, is on the monolith. Titanium dioxide has been employed as a photocatalyst in a fluid purifier to destroy contaminants. When the titanium dioxide is illuminated with ultraviolet light, photons are absorbed by the titanium dioxide, promoting an electron from the valence band to the conduction band, thus producing a hole in the valence band and adding an electron in the conduction band. The promoted electron reacts with oxygen, and the hole remaining in the valence band reacts with water, forming reactive hydroxyl radicals. When a contaminant adsorbs onto the titanium dioxide photocatalyst, the hydroxyl radicals attack and oxidize the contaminants to water, carbon dioxide, and other substances.
If only one monolith and one lamp or one bank of lamps are employed in the air purification system, much of the light from the lamp is misdirected and does not absorb onto the photocatalytic coating. Some of this misdirected light is reflected off a reflective surface applied on the housing of the air purification system and absorbed onto the photocatalytic coating. However, much of the light is still misdirected and not used for photocatalytic purposes. Therefore, the photocatalytic efficiency for the air purification system is less than optimum.
A second monolith can be positioned on the side of the lamp opposite to the first monolith to absorb the misdirected light. However, adding a second monolith is costly and light is still misdirected from the lamp and not used for photocatalytic purposes. Reflectors can be added adjacent to the lamp or bank of lamps to direct more of the light to the monolith, but this method adds an undesirable pressure drop to the system.
Hence, there is a need for a reflective lamp utilized in a fluid purification system that maximizes the light delivery to a photocatalytic coating.